Caves and other underground structures, including lava tubes, canyon overhangs, and other Martian cavities would be potentially useful for manned missions, for they would provide considerable shielding from both the elements and intense solar radiation that a Mars mission would expose astronauts to. They might also offer access to minerals, gases, ices, and any subterranean life that the crew of such a mission would probably be searching for.

The program also studied designs for inflatable modules and other such structures that would aid the astronauts to build a livable environment for humans and earth creatures.